curve_painter.dart

import 'package:flutter/material.dart';

class CurvePainter extends CustomPainter {
  final Color paintColor;

  CurvePainter(this.paintColor);

  @override
  void paint(Canvas canvas, Size size) {
    final paint = Paint();
    paint.color = paintColor;
    paint.style = PaintingStyle.fill;

    final path = Path();

    path.moveTo(0, -1);
    path.lineTo(0, size.height * 0.3);
    path.quadraticBezierTo(
      size.width * 0.1,
      size.height,
      size.width * 0.4,
      size.height * 0.7,
    );
    path.quadraticBezierTo(
      size.width * 0.8,
      size.height * 0.1,
      size.width,
      size.height * 0.91,
    );

    path.lineTo(size.width, 0);

    canvas.drawPath(path, paint);
  }

  @override
  bool shouldRepaint(CustomPainter oldDelegate) {
    return true;
  }
}